The present invention relates to brushless DC motors and, more particularly, to a drive and control circuit for single phase brushless DC motors.
Single phase brushless DC motors are commonly employed as drive motors for compact fans. Such fans are used, for example, to ventilate data processing and other electronic equipment. Operating voltages for these fans typically range from about 12 volts to over 60 volts. Unfortunately, as the operating voltage of the fan increases, the cost of the motor and its associated drive and control components causes the overall cost of the fan to exceed its selling price. This is particularly the case with fans having motors designed to operate at or near 60 volts.
Accordingly, it is an object of the present invention to provide a drive and control circuit for a brushless DC motor which not only permits the motor to operate over a broad voltage range but also reduces the overall cost of DC fans and other components incorporating such motors.
It is a further object of the invention to provide such a drive and control circuit which also provides the motor with required features such as speed control, pulse output, current limit and thermal protection.